ImmD

ImmD is a Colicin Immunity Protein produced by E. coli to protect itself from the cytotoxic tRNase domain of Colicin D. It does this by binding to the enzymatic C domain, and inhibiting its activity. Once the complex has been released and bound itself to FepA, the outer membrane receptor of the target cell, the immunity protein dissociates.

3D structures of colicin-D immunitiy protein
Colicin Immunity Protein